Matt: "Its a Therocephalian. Half mammal, half reptile-"
Becker: "All ugly."
Matt Anderson and Hilary Becker on the Therocephalians.[src]

Therocephalian were venomous, carnivorous mammal-like reptiles from the Permian and Triassic period.



Therocephalian vision. (Episode 4.4)

Therocephalians were quadrupedal creatures which were anatomically similar to Gorgonopsids, albeit with stubbier, thicker legs and a smaller body. They possessed large skulls, which were ridged from the neck, and had a broad, blunt snout with long, straight canines. Therocephalians also had a grooved ridge inside their mouth for injecting venom into their prey. When placid, Therocephalians were slow-moving, but could give surprising bouts of speed and strength when closing in on prey. Fortunately, Therocephalians were moderately weak creatures which could be easily taken down by one EMD shot.

Therocephalians lived together in large family groups consisting of dozens of members, although a rare few loners could apparently stray off from the main group. When not hunting, they spent most of their time lounging about and sleeping, although they could quickly turn deadly if any other animals disturbed them. Highly aggressive predators, when Therocephalians came across other animals, they would pursue it almost relentlessly until they closed in, at which point they would pounce upon and attack their prey with their venomous bite. (Episode 4.4)



George's arm, pre-mortem, bitten and infected by Therocephalian venom. (Episode 4.4)

Therocephalian venom was highly fast-acting and toxic on bitten animals such as humans; the poisoned bite would begin to fester almost immediately, and the victim's body would grow weaker and weaker over a matter of seconds until they were paralysed by the venom's effects, rendering them helpless to escape their Therocephalian attacker.

If a bitten victim was found before they'd been fully paralysed, the venom's spread could be halted by applying salt to the wound, saving the prey's life and giving them a chance at making a full recovery. (Episode 4.4)

Incursions and encounters

Episode 4.4

A pack of Therocephalians came through an Anomaly to McKinnon School in the present day. When a school teacher, George, tried to get a snack from a vending machine, a Therocephalian that was hiding in the machine leapt out and attacked. It bit and poisoned him, and afterwards killed him and ripped him apart. The same Therocephalian then attacked Steve and Darren in the school's security system room but failed to kill them. It then stalked Beth inside the gym, and killed her.


A nest of sleeping Therocephalians. (Episode 4.4)

It next attacked Matt Anderson but was beaten up by him, and then shot and knocked by Becker in the gym. Becker later found a nest of the other Therocephalians and accidentally woke them up. While he was shooting them back, one bit and poisoned him. Matt rescued Becker, and they tried to get out of the canteen but were overwhelmed by the Therocephalian nest; until Connor Temple, Darren and Steve gassed the Therocephalians with home-made gas bombs. It is likely that the entire nest was killed largely due to the fact that the gasses used by Connor, Darren and Steve were toxic, containing chlorine.

Real life

Therocephalians (name meaning "beast-heads") were an extinct suborder of eutheriodont therapsids, which lived from approximately 265 to 245 million years ago. They were named after their large skulls, which, along with the structure of their teeth, suggest that they were successful carnivores. The Therocephalians were more closely related to cynodonts, which would give rise to mammals, than any other group. Therocephalians lived in large numbers in what is now the Karoo of South Africa, but Therocephalian fossils have also been found in Antarctica, Russia and China.



A sleeping Therocephalian in the McKinnon School canteen. (Episode 4.4)

  • The Therocephalian was the first prehistoric creature to kill a child in Primeval.
  • Though the Therocephalians were the second venomous creatures to appear, the first being the Arthropleura, they were the first ones who were actually evidenced as being venomous.
  • The Therocephalians appeared to range in size from a small dog to a wolf, as the ones that were sleeping near the Anomaly in the canteen were a lot smaller than the one that attacked Mr. George (the ones sleeping near the Anomaly were likely younger).
  • The Therocephalians in Primeval appeared to be based on the Therocephalian in Tim Haines' previous production Walking with Monsters.
  • Because the Therocephalians were shown to sleep in bright daylight, it has been suggested that they were either nocturnal or were suffering from a form of jet lag after coming through the Anomaly.
  • The only real-life Therocephalian species to be venomous was Euchambersia, suggesting that this was the Therocephalian species featured in the show.
  • Based on the statement about the Therocephalians' venom that says that their venom is as deadly as the black mamba venom in Walking With Monsters, it's reasonable to think that the Therocephalians in Primeval had a venom that was similar to a black mamba's.


  • The size of the Therocephalian that was hiding in the vending machine would not have allowed it to fit inside the vending machine.
  • The Therocephalians in Episode 4.4 were slightly larger than real Therocephalians.
  • The Therocephalians in Primeval were depicted with external ears, when in real-life they would have had internal ears, like lizards.